Introduction
Teff Eragrostis tef (Zucc.) Trotter is a selfpollinated, annual, warm season grass that is used throughout the world as grain for human consumption and as forage for livestock. The amount of teff produced in the United States is increasing rapidly due to its popularity as a nutritious grain and high quality, horse hay.
Teff is an ancient grain that was believed to have been domesticated in Ethiopia between 4000 and 1000 BC. The grain is still a major component of the diet of millions of individuals from northeast Africa and Asian countries. When grown as a grain, it is normally ground into flour, which is used to make flat bread called injera. Teff grain does not contain gluten and is an increasingly important dietary component for individuals who suffer from gluten intolerance or Celiac disease.
In the U.S. most of the teff production is used for forage. Over the past five years, the acreage devoted to teff production has exploded, as teff is currently grown in at least 25 states across the nation.
Although the acreage devoted to grain production in the U.S. is small, the demands for teff grain from African immigrants and gluten intolerant individuals is driving the expansion of acreage.
The U.S. Environmental Protection Agency issued a finding in mid-2009 that no broadleaf herbicides were currently labeled for use on teff, as teff had assigned to the miscellaneous crop group. Crop groupings are used by the EPA as a means to reduce the number of individual crops that must be tested for pesticide residues prior to issuing an approved pesticide label. Any crop in the miscellaneous crop group must be listed specifically on a herbicide label before the product can be applied to that crop. The EPA action resulted in a severe hardship on agricultural producers who are currently growing, or would like to grow, teff grain or forage. Teff is slow to emerge and increase in size during the first 2-3 weeks of growth. It is not competitive with common summer annual broad leaved weeds typically found in grass or grain crops. Recognizing the need for additional information on herbicide safety for teff, a field trial was established near Fallon, Nev. The trial was used to evaluate several broad leaf herbicides commonly used to control weeds in grain and grass crops. The rates selected represent the upper and lower levels of normal applications of the selected chemicals. The timing of the herbicide applications were selected to represent applications at the optimal time (tillered), before (emerged) and after (boot) the optimal time of application.
Methods
The herbicides were applied to an established field of “Tiffany” teff located approximately seven miles south of Fallon, on a Stillwater slightly saline clay loam soil as described in the Fallon-Fernley Nevada Soil Survey published by the United States Department of Agriculture, Natural Resources Conservation Service. The field had been planted on June 4, 2009 and flood irrigated three times prior to the herbicide applications.
A portion of the field did not receive irrigation water during the first irrigation but was subsequently watered the second two times. The plants growing in the section of the field receiving two irrigations prior to the herbicide applications were retarded phenologically approximately two weeks as compared to plants that had received all three irrigations.
This resulted in a field that produced plants in different growth stages growing adjacent to each other. The first application (tillered) was established in an area in the field where the plants had begun to tiller at the time of the herbicide applications. The second application (emerged) was established at the same time in an adjacent area producing plants in the twofour leaf stage. The final trial was applied to plants that had reached the boot stage of growth. The teff was irrigated frequently enough that water was not limited throughout the season.
The first two trials (tillered and emerged) were applied on July 10, 2009. The third trial (boot stage) was applied on Aug. 4, 2009.
All chemicals were applied using a CO pressurized backpack sprayer. The sprayer nozzles were Teejet XR11002 spaced 15 inches apart. The materials were applied in 15 gallons of water per acre at 40 PSI. The plots were 5 feet by 10 feet in size and all treatments were replicated three times in a complete randomized block design.
The environmental conditions during the July 10, 2009 application were as follows:
- Time: 8 a.m.
- Wind: 0-1 MPH from N-NW
- Air Temperature: 68° F
- Soil Temperature @ 4”: 65° F
- Soil Moisture: Dry
- Weeds present: purslane (Portulaca oleracea L.), kochia (Kochia scoparia L. Schrad.) common mallow (Malva neglecta Wallr.), field bindweed (Convolvulus arvensis L.), lambsquarters (Chenopodium, album L.), redroot pigweed (Amaranthus retroflexus L.), and alfalfa (Medicago sativa L.)
The environmental conditions during the Aug. 4, 2009 application were as follows:
- Time: 9:00 a.m.
- Wind: 2 MPH from N
- Air Temperature: 80° F
- Soil Temperature @ 4”: 64° F
- Soil Moisture: Dry
- Weeds present: purslane (Portulaca oleracea L.), kochia (Kochia scoparia L. Schrad.) common mallow (Malva neglecta Wallr.), field bindweed (Convolvulus arvensis L.), lambsquarters (Chenopodium, album L.), redroot pigweed (Amaranthus retroflexus L.), and alfalfa (Medicago sativa L.)
Table 1 lists the chemicals and rates applied in the trials and locations. After application the plots were visually inspected weekly for signs of herbicide damage. Visual evidence of herbicide damage was not observed at any location or trial.
Table 1. Herbicides and rates applied to “Tiffany” teff in three different phenological stages
The plots were harvested when the seed heads had matured. Seed heads were considered mature when they had turned a uniform golden/straw brown color. The majority of the leaves and lower stems were green when harvest began. The trials were harvested beginning on Sept. 30, 2009 and concluded on Oct. 5, 2009.
The evaluation of the trials consisted of harvesting a 4 feet by 9 feet area from each plot using a gas powered hedge trimmer and cutting all plants at ground level. The harvested biomass from each plot was weighed and a grab sample was obtained from each plot. The grab samples were weighed, oven dried, and weighed again to determine moisture content of the biomass. All results are presented on a 100 percent dry matter basis.
Statistical analysis of the data consisted of performing an ANOVA with mean separation using Tukeys HSD at the P<0.05 level of significance.
Biomass Results
Tables 2, 3 and 4 represent biomass yields by herbicide treatment for the emerged, tillered and boot growth stage of herbicide application trials.
*No significant difference between treatments at the P<0.05 level of significance.
*No significant difference between treatments at the P<0.05 level of significance.
*No significant difference between treatments at the P <0.05 level of significance.
Conclusions
Teff biomass production was not significantly different (P<0.05) than the untreated control by any of the herbicides rates or application timing (growth stage) tested. The preliminary results indicate that all of the herbicides and rates tested were safe when applied at various growth stages of the teff plants.
Additional resources
Assefa, K., H. Tefera, A. Merker, T. Kefyalew and F. Hundera. 2001. Variability, heritability and genetic advance in phenomorphic and agronomic traits of tef [Eragrostis tef (Zucc.) Trotter germplasm from eight regions of Ethiopia. Hereditas 134:103-113.
Curtis, K.R., J. Entsminger, M. Cowee, J. Davison, and T. Harris, (2008). Market Potential for Nevada Teff Products. University Center for Economic Development (UCED) publication 2008/09-02. 38 pages.
Ketema, S. 1997. Tef. Eragrostis tef (Zucc.) Trotter. Promoting the Conservation and Use of Underutilized and Neglected Crops. Institute of Plant Genetics and Crop Plant Research, Gatersleben/International Plant Genetics Resources Institute, Rome Italy.
National Academy of Sciences, 1996. Teff. pp 215-235. In: Lost Crops of Africa. Vol. 1. Grains. Natl. Acad. Sci., Washington D.C.
Stallknecht, G.F., K.M. Gilbertson, and J.L. Eckoff. 1993. Teff: Food Crop for Humans and Animals. pp. 231-234. In: J. Jamick and J.E. Simon (eds.), New Crops. Wiley and Sons, New York.
Tefera, H. and S. Ketema. 2001. Production and importance of tef in Ethiopian Agriculture. pp 3-7. In: Tefera, H.; G. Belay and M. Sorrells (eds.) Narrowing the Rift: Tef Research and Development. Proceedings of the International Workshop on Tef Genetics and Improvement, 16-19 October 2000, Addis Ababa, Ethiopia.
